If you were to take apart an electrical socket and look at the contact
wipers that the prongs slide into, you would find that in some cases they
have bumps on them. These bumps fit into the holes so that the outlet can
grip the plug's prongs more firmly. This prevents the plug from slipping out
of the socket due to the weight of the plug and cord. It also improves the
contact between the plug and the outlet.
On Thu, 9 Aug 2012 17:53:55 -0700 (PDT), firstname.lastname@example.org
They are there for our safety. When you unplug an electrical device
there is still electricity trapped in the device and the power cord.
Those holes allow the electricity slowly dissipate harmlessly. Without
those holes life, as we know it, would cease to exist.
The LOTO hardware for a 5-15 plug us a hardened wire pin with a loop
on it and a somewhat regular looking padlock. The hasp of the lock
goes between the prongs of the plug, under the pin and through the
loop in the pin so it can't be pulled out.
This is to alert you that you are not supposed to plug it in, not
prevent the dumbest person on the planet from doing it.
In an industrial setting there is legal recourse against someone who
defeats LOTO and injures someone. It is usually only money but it is a
shitload of money.
I have spent the last 20 or more years at a place and we go over LOTO many
times during the year. The lock is not that important. It is the TAG. The
tag is to aleart others that some work is going on and it is against the
rules to defeat the tag. Just as we have some red barrier tape to be put up
around some work areas. A tag must be used to aleart people who to see if
you need to get in the tapped off area. Anyone can duck under the tape, but
if caught without your name on the tag, you can be fired.
For plugs, another way to make them safe is a plastic clam shell type of
box that goes around the plug and is then locked and tagged.
A simple plastic ty-wrap holding the tag on is just as good as the largest
lock made as far as the rules go. Everyone that goes in the plant that may
do some work goes through a safety course that lasts an hour or so. We have
several plants that are very similar in about a 100 mile area. When someone
goes from one plant to another , they go through a safety course at that
plant and get a card for that plant that is only good for a year.
We are getting away from the origional question. The holes were put in the
plugs because of the way the very old sockets were made and that hepled to
keep the plugs in the socket and make contact. They are no longer needed,
but seem to be hanging on because they were always there.
I used to work with ones that had a wire wrapped through the holes. Copper
I think. The other end of the wire went into a jato bottle with 1500 lbs of
thrust. This was for a RCAT launching rail. You removed the wire before
plugging it into some launch trigger voltage. Oh the army days....
Which came first, the chicken or the holes?
In other words, were the holes put there so that the copper wire could be
threaded through or was the copper wire threaded through based on the
convenience of the holes being present?
Remember that the original was "why we're the holes put there" not "what
are the uses of the holes".
This site offers 3 possible reasons:
I've also read that they are used by manufacturers to "lock out" the plug
prior to its initial use so that they can attach a note to say something
like "Make sure you do (insert task here) before plugging in this device."
However, I think that that's a use of them, not a reason for them.
I thought they were there to make it less likely for the plug to weld to
the socket -- sort of a "don't make the full connection all at once" thing.
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